Kay begins his piece by labeling Hart a "9/11 conspiracy theorist." In fact, anyone who thinks 9/11 was planned and carried out by more than one person must offer a theory about what is by definition a conspiracy. Therefore anyone who discusses responsibility for 9/11 is literally a conspiracy theorist. Unfortunately, this universal and thus completely empty term is often employed as an ad-hominem insult by those who have no rational or empirical arguments to back up their own conspiracy theory that 19 Arabs with box cutters and a guy in a cave on dialysis did 9/11.